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753100-601 System board for use only in models with UMA graphics, Celeron N2820 processor, and Windows 8 Professional
(includes replacement thermal materials)
756215-001 Rubber Kit for use in HP 250 models
Sequential part number listing 43
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44 Chapter 3 Illustrated parts catalog
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4 Removal and replacement procedures
Preliminary replacement requirements
You will need the following tools to complete the removal and replacement procedures:
Phillips P0 and P1 screwdrivers
The following sections include some of the considerations that you must keep in mind during disassembly
and assembly procedures.
NOTE:As you remove each subassembly from the computer, place the subassembly (and all accompanying
screws) away from the work area to prevent damage.
CAUTION:Using excessive force during disassembly and reassembly can damage plastic parts. Use care
when handling the plastic parts. Apply pressure only at the points designated in the
Cables and connectors
CAUTION:When servicing the computer, be sure that cables are placed in their proper locations during the
reassembly process. Improper cable placement can damage the computer.
Cables must be handled with extreme care to avoid damage. Apply only the tension required to unseat or
seat the cables during removal and insertion. Handle cables by the connector whenever possible. In all cases,
avoid bending, twisting, or tearing cables. Be sure that cables are routed in such a way that they cannot be
caught or snagged by parts being removed or replaced. Handle flex cables with extreme care; these cables
Preliminary replacement requirements 45
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CAUTION:Drives are fragile components that must be handled with care. To prevent damage to the
computer, damage to a drive, or loss of information, observe these precautions:
Before removing or inserting a hard drive, shut down the computer. If you are unsure whether the computer
is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
Before handling a drive, be sure that you are discharged of static electricity. While handling a drive, avoid
touching the connector.
Before removing a diskette drive or optical drive, be sure that a diskette or disc is not in the drive and be sure
that the optical drive tray is closed.
Handle drives on surfaces covered with at least one inch of shock-proof foam.
Avoid dropping drives from any height onto any surface.
After removing a hard drive, an optical drive, or a diskette drive, place it in a static-proof bag.
Avoid exposing an internal hard drive to products that have magnetic fields, such as monitors or speakers.
Avoid exposing a drive to temperature extremes or liquids.
If a drive must be mailed, place the drive in a bubble pack mailer or other suitable form of protective
packaging and label the package “FRAGILE.”
Electrostatic discharge damage
Electronic components are sensitive to electrostatic discharge (ESD). Circuitry design and structure
determine the degree of sensitivity. Networks built into many integrated circuits provide some protection,
but in many cases, ESD contains enough power to alter device parameters or melt silicon junctions.
A discharge of static electricity from a finger or other conductor can destroy static-sensitive devices or
microcircuitry. Even if the spark is neither felt nor heard, damage may have occurred.
An electronic device exposed to ESD may not be affected at all and can work perfectly throughout a normal
cycle. Or the device may function normally for a while, then degrade in the internal layers, reducing its life
CAUTION:To prevent damage to the computer when you are removing or installing internal components,
observe these precautions:
Keep components in their electrostatic-safe containers until you are ready to install them.
Before touching an electronic component, discharge static electricity by using the guidelines described in this
Avoid touching pins, leads, and circuitry. Handle electronic components as little as possible.
If you remove a component, place it in an electrostatic-safe container.
The following table shows how humidity affects the electrostatic voltage levels generated by
CAUTION:A product can be degraded by as little as 700 V.
46 Chapter 4 Removal and replacement procedures
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Typical electrostatic voltage levels
Event 10% 40% 55%
Walking across carpet 35,000 V 15,000 V 7,500 V
Walking across vinyl floor 12,000 V 5,000 V 3,000 V
Motions of bench worker 6,000 V 800 V 400 V
Removing DIPS from plastic tube 2,000 V 700 V 400 V
Removing DIPS from vinyl tray 11,500 V 4,000 V 2,000 V
Removing DIPS from Styrofoam 14,500 V 5,000 V 3,500 V
Removing bubble pack from PCB 26,500 V 20,000 V 7,000 V
Packing PCBs in foam-lined box 21,000 V 11,000 V 5,000 V
Packaging and transporting guidelines
Follow these grounding guidelines when packaging and transporting equipment:
To avoid hand contact, transport products in static-safe tubes, bags, or boxes.
Protect ESD-sensitive parts and assemblies with conductive or approved containers or packaging.
Keep ESD-sensitive parts in their containers until the parts arrive at static-free workstations.
Place items on a grounded surface before removing items from their containers.
Always be properly grounded when touching a component or assembly.
Store reusable ESD-sensitive parts from assemblies in protective packaging or non-conductive foam.
Use transporters and conveyors made of antistatic belts and roller bushings. Be sure that mechanized
equipment used for moving materials is wired to ground and that proper materials are selected to avoid
static charging. When grounding is not possible, use an ionizer to dissipate electric charges.
Follow these grounding workstation guidelines:
Cover the workstation with approved static-shielding material.
Use a wrist strap connected to a properly grounded work surface and use properly grounded tools and
Use conductive field service tools, such as cutters, screwdrivers, and vacuums.
When fixtures must directly contact dissipative surfaces, use fixtures made only of static-
Keep the work area free of nonconductive materials, such as ordinary plastic assembly aids
Handle ESD-sensitive components, parts, and assemblies by the case or PCM laminate. Handle these
items only at static-free workstations.
Preliminary replacement requirements 47